ngue to a piece of rock crystal, there is a sensation of
contact or cold, but no sense of taste. On the other hand, when we bring
the tongue in contact with a piece of rock salt, we experience the
sensations of contact, coolness, and saline taste.

Again, the mucous membrane of the mouth must be _moist_. When the mouth is
dry, and receives substances not already in solution, there is no saliva
ready to dissolve them; hence, they are tasteless. This absence of taste
is common with the parched mouth during a fever.

The tongue assists in bringing the food in contact with the nerves, by
pressing it against the roof of the mouth and the soft palate, and thus is
produced the fullest sense of taste.

319. Physiological Conditions of Taste. The tongue is the seat of
sensations which are quite unlike each other. Thus, besides the sense of
taste, there is the sensation of touch, pressure, heat and cold, burning
or acrid feelings, and those produced by the application of the tongue to
an interrupted electric current. These are distinct sensations, due to
some chemical action excited probably in the touch cells, although the
true tastes may be excited by causes not strictly chemical. Thus a smart
tap on the tongue may excite the sensation of taste.

In the majority of persons the back of the tongue is most sensitive to
bitters, and the tip to sweets. Saline matters are perceived most
distinctly at the tip, and acid substances at the sides. The nerves of
taste are sensitive in an extraordinary degree to some articles of food
and certain drugs. For example, the taste of the various preparations of
quinine, peppermint, and wild cherry is got rid of with difficulty.

Like the other special senses, that of taste may become fatigued. The
repeated tasting of one substance rapidly deadens the sensibility,
probably by over-stimulation. Some savors so impress the nerves of taste
that others fail to make any impression. This principle is used to make
disagreeable medicine somewhat tasteless. Thus a few cloves, or grains of
coffee, or a bit of pepper, eaten before a dose of castor oil, renders it
less nauseous.

Flavor is something more than taste. It is in reality a mixed
sensation, in which smell and taste are both concerned, as is shown by the
common observation that one suffering from a cold in the head, which
blunts his sense of smell, loses the proper flavor of his food. So if a
person be blindfolded, and the nose pinched, he will